1. Field of the Invention
This invention relates to computer hardware and software, and more particularly to software programs for request routing.
2. Description of the Related Art
Application servers may be part of a three-tier architecture that includes functionality for a user interface (such as a user web browser), logic execution (performed at least partially by or within the application server), and management of user session data using shared memory objects, and data storage and retrieval (such as using memory objects). Application servers may receive requests from the user interface tier (such as, but not limited to, a request for a hyper text transfer protocol (HTTP) document from a user web browser) to be fulfilled by a process on the application server. The process on the application server may require access to a session memory object in order to provide the requested information. Some requests may also cause a process to modify a memory object. For example, a request may include shopping cart list information from a client to be stored in the application server's memory object representing the client's session data and later, on getting the order request from the client, needs to be stored in a database. Therefore, the process, while storing the session data, may need to request a lock to the memory object that stores the information it needs to change to prevent another process from accessing the memory object while the process is modifying data in it.
While processing a request, the process on the application server may become hung. For example, a process may get stuck in a loop or get stuck on a portion of corrupt code. When a process becomes hung, it may hold a lock on a memory object that other processes need. In this case, the other processes may slow down or halt while they are waiting for the memory object to become available. In addition, a hung process may write corrupt data to the memory object.